Melting furnace

ABSTRACT

A melting furnace comprising a melting chamber in which a plurality of parallel adjacent electric heating resistances are transversely mounted and secured to opposite wall portions of the chamber in the region of the top thereof. The electric heating resistances have major and minor surfaces and are positioned so that their major surfaces extend parallel with the vertical plane of the melting chamber.

[ 5] Oct. 24, 1972 United States Patent Niilting [54] MELTING FURNACE[72] Inventor:

Peter Ntilting, Toging, Germany [73] Assignee: VereinigteAluminium-Werke Aktiengesellschaft, Bonn, Germany Oct. 13, 1969 Appl.No.: 865,856

358,884 10/1931 GreatBritain..........i......13/25 [22] Filed:

Primary Examiner-Leonidas Vlachos AttorneyMichael S. Striker [30]Foreign Application Priority Data Nov. 8, 1968 [57] ABSTRACT A meltingfurnace comprising a melting chamber in Germany..........P 18 07 843.8

[52] US. 13/20 which a plurality of parallel adjacent electric heating[51] Int. 7/02 resistances are transversely mounted and secured to [58]Field of Search.........266/33, 5 E, 4 E; 13/20, 25

opposite wall portions of the chamber in the region of the top thereof.The electric heating resistances have [56] References Cited UNITEDSTATES PATENTS major and minor surfaces and are positioned so that theirmajor surfaces extend parallel with the vertical plane of the meltingchamber.

2,214,123 9/1940 Delpech.................266/5 E X 2,323,051 6/194313/25 X Junker et a1. 18 Claims, 10 Drawing Figures 0/ 1 I I i I IIIIFIJl llllllkl L I l I MMMH II? U 2/ llll llw l W l 1 l l llHl lllll l rt 1. Wm ||||l| lilllllhl l ||||lll H lllll lilll l n J l ||||1|| lll r IIllllnlil MELTING FURNACE BACKGROUND OF THE INVENTION The presentinvention in general relates to a metallurgic resistance furnace andmore in particular relates to a smelting furnace of the hearth-type inwhich the heating resistors are arranged in the melting chamber of thefurnace.

Known in the art are hearth-type or reverberatory furnaces in which theheat is produced electrically and which are used for the metallurgicprocessing of, for example, aluminum or other type metals. It isconventional with such type furnaces that the electric heating elementsor resistors are located beneath the hearth and that they transformtheir energy into heat radiation to which the charge being melted orprocessed in the furnace is subjected.

Such electric heating elements or resistors are quite costly and thelife thereof is determined by two factors:

I By the operating temperature at which the element or resistor has tooperate; and

2 By the amount of splashing of the material processed, especiallyaluminum, onto the element or resistor.

In the first instance it has been found that the temperature of theelement or resistor can be maintained the lower during operationthereof, the better the element or resistor is capable of dissipatingits heat to any direction surrounding it.

In the second instance it has been found that due to splashing orspattering of the material processed, a bonding process occurs betweenthis material and the element or resistor so that oftentimes a localdisruption of the element or resistor takes place.

Certain known hearth-type furnaces employ heating elements which arefreely suspended in the melting chamber of the furnace and consist ofdouble coiled wire resistances. Such type heating elements have afavorable low operating temperature and an acceptable heat dissipation.However, such freely suspended elements, as will be self-evident, aresubject to a direct spattering attack by the material which isprocessed.

Further known hearth-type furnaces utilize zig-zag type heating elementswhich are inserted in slotted stones. Such type heating elements,however, have a poor mechanical rigidness and are operated at a hightemperature which is a disadvantage but, at the same time, such elementsare less subjected to spattering of the material processed.

In view of these disadvantages, and since no suitable compromise couldbe found to overcome the same to ensure an acceptable durability of theheating elements, the only avenue open was to resort to core-typeinduction furnaces which not only are quite expensive as regards theirprime cost, but, moreover, are extremely uneconomical as regardstheir'maintenance.

SUMMARY OF THE INVENTION Object of the invention is to provide a furnacewhich positively overcomes the above disadvantages and which is simpleas regards its construction and offers a great economy as regards itsmaintenance.

Such a furnace according to the invention comprises a melting chamberenclosed by a wall and in which a plurality of spaced heating elementsare transversely mounted in the upper region thereof, with the elementssecured to opposite wall portions of the chamber. The elements havemajor and minor surfaces and are positioned such that their majorsurfaces extend substantially parallel with the vertical plane of themelting chamber.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a top plan view of themeltingfurnace according to the present invention;

FIG. 2 is a cross-sectional view of the melting furnace taken along theline I-I. of FIG. 1;

FIG. 3 is a side view of a heating element incorporated in the furnaceof FIG. 1 and illustrating, in part, the manner of suspending thiselement in the furnace;

FIG. 4 is a cross-sectional view of a heating element taken along theline II-II of FIG. 3;

FIG. 5 is a top view of the arrangement shown in FIG. 3;

FIG. 6 is a further side view of the heating element of FIG. 3 andillustrating the manner of connecting one end thereof to the innerfurnace wall;

FIG. 7 is a top view of the arrangement of FIG. 6;

FIG. 8 illustrates. the heating element of FIG. 3, mounted in thefurnace; I

FIG. 9 is a top view of the arrangement of FIG. 8; and

FIG. 10, appearing on the sheet incorporating FIGS.

1 and 2, illustrates, in part, the manner in which the heating elementof FIG. 3 is suspended from the top of the furnace.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in detail to thedrawings, in which like reference numerals index like parts, FIGS. 1 and2 illustrate a melting furnace l which includes a melting chamber 2enclosed by a wall 3. Provided at one end of the 'fumace 1 is a doorarrangement 4 operative to admit material to be processed into themelting chamber 2.

Horizontally mounted in the upper region 5 of the melting chamber 2 andsecured to inner opposite wall portions 6 and 7 thereof, are a pluralityof parallel spaced discrete electric heating elements 8.

The heating elements 8 are substantially straight, and as shown in FIG.4, have a T-shaped cross section with major and minor surfaces 9 and 10,respectively. The height of the major surfaces 9 of the heating elements8 is substantially greater than the width of the minor surfaces 10 ofthe elements, and the latter are mounted in such a way in the meltingfurnace 1, that their major surfaces 9 extend substantially parallelwith the vertical axis of the furnace 1 while their minor surfaces 10extend substantially parallel with the horizontal axis of the furnace 1.

Also, as shown in FIG. 1, the heating elements 8 are positionedtransversely relative to the elongation of the melting furnace.

Each two adjacent electric heating elements 8 at their respective outerends, are pair-wise interconnected by means of band-shaped electriccross connectors l1 and thus formed into an electrically serieswoundgroup 12. Shown in straight lines in FIG. 1, at the left-hand sidethereof, is such a pair of interconnected heating elements 8. The restof these interconnected elements 8 are shown in broken lines.

In the present embodiment and as shown in FIG. 1, the electric heatingelements 8 are operated by an AC- current and, in order to constitute asymmetric loading of the three phases R, S, T of the AC-power system,the elements 8 are formed into three electrically serieswound groups 12.

However, also 6 or even 9 groups of series-wound electric heatingelements 8 may be used depending on the size of the melting furnace.

The manner of interconnecting the respective serieswound groups 12 withthe AC-power system will be explained shortly.

As shown in FIGS. 1, 2, 8 and 9, the cross connectors 11 at one side ofthe heating elements 8, are slightly spaced from the inner wall portion6, inwards of the outer ends 13 of the elements 8 such that these outerends 13 extend beyond the cross connectors 11.

Formed in wall portion 6 are a plurality of recesses 14 in which theouter ends 13 of the heating elements 8 are received.

Likewise as regards the heating elements 8, these recesses 14 in thewall 6 extend parallel and spaced relative to each other andtransversely relative to the elongation of the melting chamber 2.

Upon insertion of the outer ends 13 into the recesses 14, the latter arestuffed with insulation stones and mineral wool, not shown, in order toobtain a better thermal insulation.

The opposite wall portion 7 is formed with an equal number of recesses15 which extend substantially axially with the recesses 14in wallportion 6.

The recesses 15 are arranged to fixedly mount a plurality of supportingprojections 16 whose number equals that of the electric heating elements8. At their projecting ends, the supporting projections 16, made of anon-scaling material, are formed with indentations 17 at their upperedge 16a, FIG. 6, in which the outer end portions 18, FIG. 7, ofcylindrical or round bolts 19 are snugly but removably fitted.

The cylindrical bolts 19 are welded to the end portions 20 of theelectric heating elements 3 and are attached thereto in such a way thatthey replace a portion of the major surfaces 9 at these end portions 20of the heating elements 8, FIG. 6.

The cross connectors 11, at this side of the heating elements 8, aresecured to the end portions 20 thereof, adjacent the bolts 19 and are ofsuch a length that they interfit between each two inner opposing majorsurfaces 9 of each two adjacent heating elements 8, FIGS. 7 and 9, whilethe outer end portions 18 are longer than the cross connectors 1 1 andextend laterally outwardly beyond each two minor surfaces of each twoadjacent heating elements 8, FIGS. '7 and 9.

Upon insertion of the supporting projections 16 into the recesses 15,the latter are stuffed with insulation stones to obtain a better thermalinsulation and to prevent tilting of the supporting projections'16therein.

In addition to the above-described manner of laterally supporting thediscrete heating elements 8, the latter are futher supported bysuspension members 21, FIG. 2.

Depending upon the length of the melting chamber 2, the discreteelectric heating elements 8 are preferably suspended in spacedrelationship of about 20 inches relative to each other by means of thesuspension members 21. This, of course, means that also the recesses 14and 15 in the walls 6 and 7, respectively, are spaced about 20 inchesapart relative to each other. The suspension members 21, made ofheat-resisting rods, at their lower ends are flat-forged and arekey-wise inserted with these ends into slotted holes 22 arrangedcentrally in the minor surfaces 10 midway of the heating elements 8,FIGS. 3 and 5, and by rotation through 90 in holes 22, are fittedlysecured against removal therefrom.

As shown in FIG. 10, upwardly the suspension members 21 are run throughguide tubes 23 which extend through the top 24 of the melting furnace 1.The upper projecting ends 21a of the member 21 are locked in position bymeans of split pins 25 which abut against profrilated bricks 26,supported on the steel housing 27 of the upper furnace surface.

In this manner, the weight of the heating elements is not suspended fromthe inner surface of the furnace top 24, which has the advantage that amore rigid and reliable suspension is obtained while, in addition, withthis manner of suspension, contact between the heating elements 8 andthe steel housing 27 is avoided.

It is a basic characteristic of the subject invention to provide thediscrete electric heating elements 8 with as great a mechanical sectionmodulus and rigidity as possible so as to keep the suspension, andthereby the number of suspension members 21 for each discrete heatingelement 8, at a low minimum.

It has been found that as a result of the general configuration of theelectric T-shaped heating elements 8, i.e., their large major surfaces 9and smaller minor surfaces 10, the mechanical section modulus thereof isconsiderably increased while, simultaneously, and again as a result oftheir physical configuration, the same are exceptionally non-reactive tosplashing or spattering of the material processed in the furnace.

As shown in FIG. 1, each group of series-wound heating elements 12 isconnected with the secondary of a transformer 28 via terminal connectors29 and guiderails 30 while the primary of the transformer is connectedwith an AC-power system, not shown.

It will be appreciated that the large cross-sectional area of thediscrete electric heating elements effects a low electric resistance permm, which enables that the heating elements can be advantageouslyoperated at a low voltage and high amperage.

The electric heating elements 8, the electric cross connectors 11 andthe terminal connectors 29 preferably are welded to each other while theterminal connectors 29, the guide-rails 30 and the terminal clamps ofthe transformers 28 are threadably connected to each other by means ofscrew members.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

Iclaim:

1. A wall furnace comprising a bottom wall, side walls and a roofdefining a melting chamber of an uninterrupted space between said bottomwall and said roof adapted to receive in a lower part of said space amass of molten material; heating means in said melting chamber forheating the interior thereof and comprising a plurality of spacedheating elements of uniform cross section throughout their length andextending in an upper region of said space transversely between oppositeside walls, each of said heating elements having a T-shaped crosssection comprising an upper horizontally extending portion and a narrowweb portion extending vertically downwardly midway between opposite endsof said horizontally extending portion and having a height considerablygreater than the width of said horizontally extending portion to thusreduce the surface areas of said heating elements which are subjected tospattering of molten material in the lower part of said space whileimproving the bending resistance of said heating elements; and meanssecuring each of said plurality of heating elements to opposite sidewalls of said melting furnace.

2. A furnace as defined in claim 1, wherein said melting chamber iselongated and wherein said heating elements extend substantiallyparallel relative to each other and substantially transversely relativeto the elongation of said hollow melting chamber.

3. A furnace as defined in claim 2 wherein said heating elements aresubstantially rectilinear.

4. A furnace as defined in claim 1 wherein said plurality of heatingelements are connected in series.

5. A furnace as defined in claim 1 wherein said plurality of heatingelements are electric resistance elements.

6. A furnace as defined in claim 1 wherein said pin rality of heatingelements are electric resistance elements and wherein said heating meansalso includes electric current transformer means interconnected withsaid electric resistance elements.

7. A furnace as defined in claim 6, wherein said electric currenttransformer means are secured to said melting furnace exteriorly of saidmelting chamber.

8. A furnace as defined in claim 1, wherein said melting chamber iselongated and said side walls include a first wall and a second wallextending in the direction of elongation of said melting chamber, andwherein said securing means includes a plurality of recesses formed insaid first wall and said second wall and operative to connect saidT-shaped heating elements at opposite end portions thereof to said firstand second walls.

9. A furnace as defined in claim 8, wherein said T- shaped heatingelements with one of said opposite end portions thereof is fixedlymounted in said recesses in said first wall, and wherein said securingmeans further includes a plurality of supporting members fixedly mountedin said recesses in said second wall and supporting said T-shapedheating elements at the second end ortion thereof;

1 A furnace as defined in claim 9, wherein said recesses in said firstand second walls extend substantially parallel and adjacent each otherin said direction of elongation of said melting chamber.

11. A furnace as defined in claim 10, wherein said recesses in saidfirst wall extend substantially axially with said recesses in saidsecond wall.

1 2. A furnace as defined in claim 4, wherein said plurality of heatingelements connected in series are electric heating elements, and whereineach two adjacent electric heating elements are interconnected by meansupper ends are run through said roof and retained at said upper ends atthe upper surface of said roof exteriorly of said furnace.

16. A furnace as defined in claim 15, wherein said rod-shaped suspensionmembers at the lower end thereof are anchored in said plurality ofspaced heating elements to thereby suspend the same.

17. A furnace as defined in claim 16, wherein each of said spacedheating elements is suspended by at least one of said rod-shapedsuspension members.

18. A furnace as defined in claim 15, wherein said upper ends of saidrod-shaped suspension members run through said roof are electricallyinsulated at said upper exterior surface of said roof.

1. A wall furnace comprising a bottom wall, side walls and a roofdefining a melting chamber of an uninterrupted space between said bottomwall and said roof adapted to receive in a lower part of said space amass of molten material; heating means in said melting chamber forheating the interior thereof and comprising a plurality of spacedheating elements of uniform cross section throughout their length andextending in an upper region of said space transversely between oppositeside walls, each of said heating elements having a T-shaped crosssection comprising an upper horizontally extending portion and a narrowweb portion extending vertically downwardly midway between opposite endsof said horizontally extending portion and having a height considerablygreater than the width of said horizontally extending portion to thusreduce the surface areas of said heating elements which are subjected tospattering of molten material in the lower part of said space whileimproving the bending resistance of said heating elements; and meanssecuring each of said plurality of heating elements to opposite sidewalls of said melting furnace.
 2. A furnace as defined in claim 1,wherein said melting chamber is elongated and wherein said heatingelements extend substantially parallel relative to each other andsubstantially transversely relative to the elongation of said hollowmelting chamber.
 3. A furnace as defined in claim 2 wherein said heatingelements are substantially rectilinear.
 4. A furnace as defined in claim1 wherein said plurality of heating elements are connected in series. 5.A furnace as defined in claim 1 wherein said plurality of heatingelements are electric resistance elements.
 6. A furnace as defined inclaim 1 wherein said plurality of heating elements are electricresistance elements and wherein said heating means also includeselectric current transformer means interConnected with said electricresistance elements.
 7. A furnace as defined in claim 6, wherein saidelectric current transformer means are secured to said melting furnaceexteriorly of said melting chamber.
 8. A furnace as defined in claim 1,wherein said melting chamber is elongated and said side walls include afirst wall and a second wall extending in the direction of elongation ofsaid melting chamber, and wherein said securing means includes aplurality of recesses formed in said first wall and said second wall andoperative to connect said T-shaped heating elements at opposite endportions thereof to said first and second walls.
 9. A furnace as definedin claim 8, wherein said T-shaped heating elements with one of saidopposite end portions thereof is fixedly mounted in said recesses insaid first wall, and wherein said securing means further includes aplurality of supporting members fixedly mounted in said recesses in saidsecond wall and supporting said T-shaped heating elements at the secondend portion thereof.
 10. A furnace as defined in claim 9, wherein saidrecesses in said first and second walls extend substantially paralleland adjacent each other in said direction of elongation of said meltingchamber.
 11. A furnace as defined in claim 10, wherein said recesses insaid first wall extend substantially axially with said recesses in saidsecond wall.
 12. A furnace as defined in claim 4, wherein said pluralityof heating elements connected in series are electric heating elements,and wherein each two adjacent electric heating elements areinterconnected by means of electric cross connectors.
 13. A furnace asdefined in claim 1, and including suspension members for suspending saidplurality of spaced heating elements intermediate the ends thereof inthe upper region of said melting chamber.
 14. A furnace as defined inclaim 13, wherein said suspension members suspend said plurality ofspaced heating elements from said roof.
 15. A furnace as defined inclaim 14, wherein said suspension members are rod-shaped and with theirupper ends are run through said roof and retained at said upper ends atthe upper surface of said roof exteriorly of said furnace.
 16. A furnaceas defined in claim 15, wherein said rod-shaped suspension members atthe lower end thereof are anchored in said plurality of spaced heatingelements to thereby suspend the same.
 17. A furnace as defined in claim16, wherein each of said spaced heating elements is suspended by atleast one of said rod-shaped suspension members.
 18. A furnace asdefined in claim 15, wherein said upper ends of said rod-shapedsuspension members run through said roof are electrically insulated atsaid upper exterior surface of said roof.